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Spec Evo Guide: Phylogeny
To succeed in spec evo, an important thing to know is how different groups of organisms relate to each other. Often, this can be quite confusing, so this page is a rough guide to phylogeny. This focuses on animals, as other kingdoms are not my expertise. However, anyone with expertise on plants, fungi, bacteria, or other kingdoms may edit this to include these kingdoms. First, here are a few pointers when creating/using taxon names. Try to make all taxa clades, unless this is completely impossible, such as an entire order of animals stemming from a single species, but mention that the common ancestor of this group is that species, thus calling it a clade. Don't use paraphyletic groupings (such as Pelycosauria, lizards, monkeys, invertebrates, etc.) or polyphyletic ones (such as algae, Protozoa, warm-blooded animals, etc.). When naming any clade with a rank from superfamily to subtribe in the case of animals (in some cases infratribe, but this is not officially recognized; infrafamily is also unrecognized), use correct terminations. These are -oidea, -idae, -inae, -ini, and -ina, for superfamily, family, subfamily, tribe, and subtribe, respectively. Also, remember to use Latin or Greek roots when giving formal names to species or clades. Also note that "taxon" is an alternative/favourable word over "genus" and "species" under phylogeny/cladistics. Now, with that out of the way, here is a guide to phylogeny. Above the Kingdom Level Starting at the top level, the original split of organisms occurred between bacteria and the all other organisms, the Archaea included. The next split was between the Archaea and the eukaryotes. Animals and fungi are within the Unikonta, and within that clade the Opisthokonta. In these clades there are also various protozoans, which are a polyphyletic group. Besides the Unikonta, the other large eukaryote groups are the Amoebozoa and the Bikonta, which includes the Protophyta and algae (both polyphyletic groups), as well as the plants. Animalia Although this is not completely proven, the most basal animal phylum is likely to be the Porifera, or sponges. Their bodies are not separated into tissues, and the adults are completely sessile. Other, more radical, hypotheses include Ctenophora being the most basal phylum, but they share so many characteristics with the Cnidaria that it is unlikely that these features evolved independently. Also, Porifera are known from the fossil record from up to 760 million years ago (before either glaciation of the Cryogenian). Some scientists considered these finds to be dubious, but even if they are not sponges they are known from at least the Ediacaran. Bilateria and Radiata After the rest of the animals diverged from the Porifera, they diverged into two main lineages, the Bilateria and Radiata. The Bilateria includes most living animals, and the Radiata includes radially symmetric animals. Recently, Radiata has been revised to be a clade, and now excludes the Porifera and Echinodermata, leaving only the Cnidarian and Ctenophora. Within the Bilateria, there are two main groups, the Deuterostomia, and the much more diverse Protostomia. In the Radiata, the two main groups are the Ctenophora, or comb jellies; and the Cnidaria, including jellyfish, sea anemones, and corals. Protostomia The Protostomia is the most diverse group of animals above the phylum level. It can be divided into three superphyla, the Ecdysozoa, the Lophotrochozoa, and the Platyzoa. The Ecdysozoa includes the familiar arthropods, the somewhat well known tardigrades and nematodes, and several lesser known phyla. The Lophotrochozoa is composed of the familiar molluscs and annelids, and other lesser known phyla, such as the brachiopods and the bryozoans. The Platyzoa contains the familiar flatworms, or Platyhelmithes, and other unfamiliar phyla, such as the microscopic rotifers. Deuterostomia Although less diverse than the protostomes, the deuterostomes include the vertebrates, likely the most successful group in animal history. Besides the vertebrates and other chordates, the Deuterostoma includes the Echinodermata and Hemichordata. Since these last two phyla do not have complicated evolutionary relationships, they will be detailed here. Echinodermata Besides several extinct groups, the Echinodermata includes three main extant groups – the Crinozoa, the Asterozoa, and the Echinozoa. The Crinozoa includes the sessile crinoids (Crinoidea), and several other extinct classes. The Asterozoa includes the sea stars (Asteroidea) and the brittle stars (Ophiuroidea). In turn, the Ophiuroidea includes two main groups, the true brittle stars and the larger basket stars. The Echinozoa includes the sea urchins and sand dollars (Echinoidea), as well as the sea cucumbers (Holothuroidea). Hemichordata The Hemichordata are considered the sister taxon to the Echinodermata, and have simple evolutionary relationships. They are composed of the classes Enteropneusta (acorn worms) and the Pterobranchia. They are generally considered to be a type of marine worm, although the marine worm group is polyphyletic and is a useless taxon. Category:Projects Category:Community Projects